A fireplace in a home or other building commonly is connected by a generally vertical chimney flue to the outside of the building. Smoke from the fire therefore passes up the flue to the outside, as desired. Most fireplaces additionally are provided with a damper which can be closed to restrict air flow through the chimney flue when the fireplace is not being used. Traditionally these dampers have been installed near the base of the flue, but more recently models have been devised for installation at the top of the flue as well.
Traditional dampers installed near the base of flue often do not adequately seal the air passageway, therefore allowing considerable cold air to enter the dwelling even when the damper is in the closed position.
Dampers constructed to be installed at the top of a flue have been somewhat more successful in sealing the air passageway, but at the expense of considerable mechanical apparatus which involves excessive cost, weight, and proneness to failure, particularly under the extreme temperature variations which accompany fireplace use. Reference is made to U.S. Pat. No. 4,020,754, which describes one such damper. Damper devices located at the top of a flue typically include a spring for urging the damper open. Such springs and their accompanying apparatus are subjected to high temperatures during use of the fireplace, and to even higher temperatures in the event of a chimney fire. Such temperatures can damage the damper, changing the normal, relaxed position of the spring, and eliminating or reducing the ability of the spring to function properly.